(A) Field of the Invention
The present invention relates to an ozone generator, particularly to an ozone generator which can reduce the amount of NOx (including NO to and NO2) produced.
(B) Description of Related Art
Basically, ozone is a widely used substance and can be used for sterilization, deodorization, decolorization, air purification, water treatment and food treatment etc. As a consequence, the use of a ozone generator becomes very popular. The principles frequently used for generating ozone in the ozone generators include high-voltage discharge and ultra-violet radiation. Due to cost consideration, a commercially available and industrially applicable ozone generator employing the principle of high-voltage discharge is most popular.
The principle of high-voltage discharge can be briefly described as follows. When air is supplied to an electric field, the oxygen molecule therein will be dissociated into oxygen atoms, as shown in the following formula (A). The oxygen atom then combines with a surrounding oxygen molecule to produce ozone, as shown in the following formula (B). However, the oxygen atom will also combine with a surrounding nitrogen molecule to produce nitric oxide at the same time as producing ozone. The nitride oxide will recombine with ozone and thus generate NO2 (nitrogen dioxide), as shown in the following formulas (C) and (D). 
Reaction in formula (D) is very fast. Most of NO can be converted into NO2 in the reaction zone. The concentration of the incidentally produced NO2 is too high. Long-term exposure of 0.05xcx9c0.1 ppm NO2 will increase the possibility of having chronic tracheobronchitis, for example, Furthermore, a person could develop respiratory tract obstruction as well as tracheobronchitis if exposed to an environment with a higher concentration ( greater than 2.5 ppm) of NO2.
The conventional ozone generators (air purifiers) are, however, unable to control the amount of NO2 produced, and thus a relatively high amount of NO2 is produced therefrom so that human body is adversely affected. It can be shown from the test results illustrated in the table below of various brands of ozone generators.
The object of the present invention is to provide an ozone generator with a low production amount of NOx. Basically, the amount of NOx produced by the present invention is reduced by lowering the temperature of the area where the ozone reaction is conducted, by controlling the voltage, and by increasing the velocity of air passing through.
According to the principle of production of NOx, the higher the temperature of the chemical reaction is, the greater the production of NOx is. As long as the reaction temperature can be controlled at a lower level, the production of NOx can be reduced.
Moreover, another factor affecting the production of NOx is the plate electric field. Since the concentration of oxygen atoms can be controlled by properly controlling the voltage, if the voltage were controlled properly, the production of NOx could be successfully reduced accordingly. This can be shown from the test results illustrated in the table below.
Furthermore, from a kinetic point of view, the shorter the reaction time in the plate discharging area is, the less the concentration of NOx produced. The quicker the flow rate of the air is, the shorter the reaction time is. Thus, increasing the velocity of air passing through can reduce the production of NOx.
To achieve the object mentioned above, the ozone generator with reduced NOx disclosed in the present invention comprises an air stream generating means for producing an air stream with a specific flow rate; a drying means for dehumidify the air stream; an electrical field generating unit for generating an electrical field, at the downstream side of the air stream of the air stream generating means; a high voltage generating means for providing the electrical field generating unit with a high voltage being capable of generating ozone; and a cooling means for lowering the temperature of the air stream to allow the ozone to be produced in a lowered environment temperature.
With the construction described above, the amount of nitric oxide produced along with ozone will be controlled and will be in such a low concentration as to cause no harm to the human body.
The present invention also provides a method which applies to the ozone generator of the present invention, comprising steps as follows:
(a) introducing an air stream into the ozone generator;
(b) drying the air stream with a drying means, and then accelerating the air stream to a flow rate of more than 700 s.c.c.m. (standard cubic centimeters per minute) with an air stream generating means;
(c) cooling down the air stream to under 10xc2x0 C. with a cooling means, the cooling means is a coolant or a thermoelectric cooler; and
(d) passing the air stream through an electrical field to generate ozone.